Planetary gear train of automatic transmission for vehicle

ABSTRACT

A planetary gear train of an automatic transmission for a vehicle may include an input shaft to receive an engine torque, an output shaft to output a shifted torque, a first planetary gear set including a first rotation element, a second rotation element, and a third rotation element, a second planetary gear set including a fourth rotation element, a fifth rotation element, and a sixth rotation element, a third planetary gear set including a seventh rotation element, an eighth rotation element, and a ninth rotation element, a fourth planetary gear set including a tenth rotation element, an eleventh rotation element, and a twelfth rotation element, and six control elements for selectively interconnecting the rotation elements and a transmission housing.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2015-0145634, filed Oct. 19, 2015, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an automatic transmission for a vehicle.

Description of Related Art

Recent increases in oil prices are triggering stiff competition among auto-makers in enhancing fuel consumption of a vehicle.

Therefore, research is being conducted on engines in terms of reducing weight and improving fuel efficiency by down-sizing, and research is also being conducted to ensure both drivability and competitiveness for maximizing fuel efficiency by implementing an automatic transmission with multiple speed stages.

However, in the case of the automatic transmission, the number of internal components increases as the number of gear shift stages is increased, which may deteriorate installability, production cost, weight and/or power flow efficiency.

Therefore, in order to maximally enhance fuel consumption of an automatic transmission having more shift stages, it is important for better efficiency to be derived by a smaller number of parts.

In this respect, an eight-speed automatic transmission has been recently introduced, and a planetary gear train for an automatic transmission enabling more shift stages is under investigation.

Considering that gear ratio spans of recently developed eight-speed automatic transmissions are typically between 6.5 and 7.5, fuel consumption enhancement is not very large.

In the case of a gear ratio span of an eight-speed automatic transmission having a level above 9.0, it is difficult to maintain step ratios between adjacent shift stages to be linear, by which driving efficiency of an engine and drivability of a vehicle are deteriorated.

Thus, research studies are underway for developing a high efficiency automatic transmission having nine or more speeds.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing a planetary gear train of an automatic transmission for a vehicle having advantages of, by minimal complexity, realizing at least nine forward speeds and at least one reverse speed, increasing a gear ratio span so as to improve power delivery performance and fuel consumption, and achieving linearity of shift-stage step ratios.

According to various aspects of the present invention, a planetary gear train of an automatic transmission for a vehicle may include an input shaft to receive an engine torque, an output shaft to output a shifted torque, a first planetary gear set including first, second, and third rotation elements, a second planetary gear set including fourth, fifth, and sixth rotation elements, a third planetary gear set including seventh, eighth, and ninth rotation elements, a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements, and six control elements for selectively interconnecting the rotation elements and a transmission housing, in which the input shaft may be continuously connected with the third rotation element, the output shaft may be continuously connected with the twelfth rotation element, the fourth rotation element may be directly connected with the transmission housing, the second rotation element may be continuously connected with the ninth rotation element, the second rotation element may be continuously connected with the tenth rotation element, the fifth rotation element may be continuously connected with the twelfth rotation element, the seventh rotation element may be selectively connectable with the transmission housing, and three control elements of the six control elements may be operated in order to achieve at least nine forward speeds and at least one reverse speed.

The eighth rotation element may be selectively connectable with the transmission housing, the input shaft may be selectively connectable with the seventh rotation element, the input shaft may be selectively connectable with the eleventh rotation element, the second rotation element may be selectively connectable with the sixth rotation element, and the first rotation element may be selectively connectable with the seventh rotation element.

The first, second, and third rotation elements may be a sun gear, a planet carrier, and a ring gear of the first planetary gear set, the fourth, fifth, and sixth rotation elements may be a sun gear, a planet carrier, and a ring gear of the second planetary gear set, the seventh, eighth, and ninth rotation elements may be a sun gear, a planet carrier, and a ring gear of the third planetary gear set, and the tenth, eleventh, and twelfth rotation elements may be a sun gear, a planet carrier, and a ring gear of the fourth planetary gear set.

According to various aspects of the present invention, a planetary gear train of an automatic transmission for a vehicle may be an input shaft receiving an engine torque, an output shaft outputting a shifted torque, a first planetary gear set including first, second, and third rotation elements, a second planetary gear set including fourth, fifth, and sixth rotation elements, a third planetary gear set including seventh, eighth, and ninth rotation elements, a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements, six control elements for selectively interconnecting the rotation elements and a transmission housing, a first connecting member connected with the first rotation element, a second connecting member connected with the second rotation element, the ninth rotation element, and the tenth rotation element, a third connecting member connected with the third rotation element and directly connected with the input shaft, a fourth connecting member connected with the fourth rotation element and directly connected with the transmission housing, a fifth connecting member connected with the fifth rotation element and the twelfth rotation element and directly connected with the output shaft, a sixth connecting member connected with the sixth rotation element and selectively connectable with the second connecting member, a seventh connecting member connected with the seventh rotation element, selectively connectable with the input shaft and the first connecting member, and selectively connectable with the transmission housing, an eighth connecting member connected with the eighth rotation element and selectively connectable with the transmission housing, and a ninth connecting member connected with the eleventh rotation element and selectively connectable with the input shaft.

The first planetary gear set may be a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear, where the first rotation element may be the first sun gear, the second rotation element may be the first planet carrier, and the third rotation element may be the first ring gear, the second planetary gear set may be a single pinion planetary gear set including a second sun gear, a second planet carrier, and a second ring gear, where the fourth rotation element may be the second sun gear, the fifth rotation element may be the second planet carrier, and the sixth rotation element may be the second ring gear, the third planetary gear set may be a single pinion planetary gear set including a third sun gear, a third planet carrier, and a third ring gear, where the seventh rotation element may be the third sun gear, the eighth rotation element may be the third planet carrier, and the ninth rotation element may be the third ring gear, and the fourth planetary gear set may be a single pinion planetary gear set including a fourth sun gear, a fourth planet carrier, and a fourth ring gear, where the tenth rotation element may be the fourth sun gear, the eleventh rotation element may be the fourth planet carrier, and the twelfth rotation element may be the fourth ring gear.

The six control elements may include a first clutch selectively connecting the input shaft and the seventh connecting member, a second clutch selectively connecting the input shaft and the ninth connecting member, a third clutch selectively connecting the second connecting member and the sixth connecting member, a fourth clutch selectively connecting the first connecting member and the seventh connecting member, a first brake selectively connecting the seventh connecting member and the transmission housing, and a second brake selectively connecting the eighth connecting member and the transmission housing.

Shift stages realized by selective operation of the six control elements may be a first forward speed realized by operation of the third and fourth clutches and the second brake, a second forward speed realized by operation of the third and fourth clutches and the first brake, a third forward speed realized by operation of the first, third, and fourth clutches, a fourth forward speed realized by operation of the first, second, and third clutches, a fifth forward speed realized by operation of the first, second, and fourth clutches, a sixth forward speed realized by operation of the second and fourth clutches and the first brake, a seventh forward speed realized by operation of the second and fourth clutches and the second brake, an eighth forward speed realized by operation of the second clutch and the first and second brakes, a ninth forward speed realized by operation of the first and second clutches and the second brake, and a reverse speed realized by operation of the first and third clutches and the second brake.

According to various aspects of the present invention, a planetary gear train of an automatic transmission for a vehicle may include an input shaft for receiving an engine torque, an output shaft for outputting a shifted torque, a first planetary gear set being a single pinion planetary gear set and including first, second, and third rotation elements, a second planetary gear set being a single pinion planetary gear set including fourth, fifth, and sixth rotation elements, a third planetary gear set being a single pinion planetary gear set and including seventh, eighth, and ninth rotation elements, a fourth planetary gear set being a single pinion planetary gear set and including tenth, eleventh, and twelfth rotation elements, a first connecting member connected with the first rotation element, a second connecting member connected with the second rotation element, the ninth rotation element, and the tenth rotation element, a third connecting member connected with the third rotation element and directly connected with the input shaft, a fourth connecting member connected with the fourth rotation element and directly connected with the transmission housing, a fifth connecting member connected with the fifth rotation element and the twelfth rotation element and directly connected with the output shaft, a sixth connecting member connected with the sixth rotation element and selectively connectable with the second connecting member, a seventh connecting member connected with the seventh rotation element, selectively connectable with the input shaft and the first connecting member, and selectively connectable with the transmission housing, an eighth connecting member connected with the eighth rotation element and selectively connectable with the transmission housing, a ninth connecting member connected with the eleventh rotation element and selectively connectable with the input shaft, a first clutch selectively connecting the input shaft and the seventh connecting member, a second clutch selectively connecting the input shaft and the ninth connecting member, a third clutch selectively connecting the second connecting member and the sixth connecting member, a fourth clutch selectively connecting the first connecting member and the seventh connecting member, a first brake selectively connecting the seventh connecting member and the transmission housing, and a second brake selectively connecting the eighth connecting member and the transmission housing.

The first planetary gear set may include a first sun gear, a first planet carrier, and a first ring gear, where the first rotation element may be the first sun gear, the second rotation element may be the first planet carrier, and the third rotation element may be the first ring gear, the second planetary gear set includes a second sun gear, a second planet carrier, and a second ring gear, where the fourth rotation element may be the second sun gear, the fifth rotation element may be the second planet carrier, and the sixth rotation element may be the second ring gear, the third planetary gear set includes a third sun gear, a third planet carrier, and a third ring gear, where the seventh rotation element may be the third sun gear, the eighth rotation element may be the third planet carrier, and the ninth rotation element may be the third ring gear, and the fourth planetary gear set includes a fourth sun gear, a fourth planet carrier, and a fourth ring gear, where the tenth rotation element may be the fourth sun gear, the eleventh rotation element may be the fourth planet carrier, and the twelfth rotation element may be the fourth ring gear.

According to various aspects of the present invention, a planetary gear train of an automatic transmission for a vehicle may include an input shaft for receiving an engine torque, an output shaft for outputting a shifted torque, a first planetary gear set comprising a single pinion planetary gear set and including a first sun gear, a first planet carrier, and a first ring gear, a second planetary gear set comprising a single pinion planetary gear set and including a second sun gear, a second planet carrier, and a second ring gear, a third planetary gear set comprising a single pinion planetary gear set and including a third sun gear, a third planet carrier, and a third ring gear, a fourth planetary gear set comprising a single pinion planetary gear set and including a fourth sun gear, a fourth planet carrier, and a fourth ring gear, a first connecting member connected with the first sun gear, a second connecting member connected with the first planet carrier, the third ring gear, and the fourth sun gear, a third connecting member connected with the first ring gear and directly connected with the input shaft, a fourth connecting member connected with the second sun gear and directly connected with a transmission housing, a fifth connecting member connected with the second planet carrier and the fourth ring gear and directly connected with the output shaft, a sixth connecting member connected with the second ring gear and selectively connectable with the second connecting member, a seventh connecting member connected with the third sun gear, selectively connectable with the input shaft and the first connecting member, and selectively connectable with the transmission housing, an eighth connecting member connected with the third planet carrier and selectively connectable with the transmission housing, a ninth connecting member connected with the fourth planet carrier and selectively connectable with the input shaft, and six control elements for selectively interconnecting the connecting members and the transmission housing. A planetary gear train according to various embodiments of the present invention realizes at least nine forward speeds and at least one reverse speed formed by operating the four planetary gear sets as simple planetary gear sets by controlling six control elements.

In addition, a planetary gear train according to various embodiments of the present invention realizes a gear ratio span of more than 8.0, thereby maximizing efficiency of driving an engine.

Furthermore, the linearity of step ratios of shift stages is secured while multi-staging the shift stage with high efficiency, thereby making it possible to improve drivability such as acceleration before and after a shift, an engine speed rhythmic sense, and the like.

It is understood that the term “vehicle” or “vehicular” or other similar terms as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuel derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example, both gasoline-powered and electric-powered vehicles.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a planetary gear train according to various embodiments of the present invention.

FIG. 2 is operational chart for respective control elements at respective shift stages in the planetary gear train according to various embodiments of the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

FIG. 1 is a schematic diagram of a planetary gear train according to various embodiments of the present invention.

Referring to FIG. 1, a planetary gear train according to various embodiments of the present invention includes first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4 arranged on a same axis, an input shaft IS, an output shaft OS, nine connecting members TM1 to TM9 for interconnecting rotation elements of the first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, six control elements C1 to C4 and B1 to B2, and a transmission housing H.

Torque input from the input shaft IS is shifted by cooperative operation of the first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, and then output through the output shaft OS.

The simple planetary gear sets PG1, PG2, PG3, and PG4 are arranged in the order of first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, from an engine side.

The input shaft IS is an input member, and the torque from a crankshaft of an engine, after being torque-converted through a torque converter, is input into the input shaft IS.

The output shaft OS is an output member, and being arranged on a same axis with the input shaft IS, delivers a shifted torque to a drive shaft through a differential apparatus.

The first planetary gear set PG1 is a single pinion planetary gear set, and includes a first sun gear S1, a first planet carrier PC1 that supports a first pinion P1 externally engaged with the first sun gear S1, and a first ring gear R1 internally engaged with the first pinion P1. The first sun gear S1 acts as a first rotation element N1, the first planet carrier PC1 acts as a second rotation element N2, and the first ring gear R1 acts as a third rotation element N3.

The second planetary gear set PG2 is a single pinion planetary gear set, and includes a second sun gear S2, a second planet carrier PC2 that supports a second pinion P2 externally engaged with the second sun gear S2, and a second ring gear R2 internally engaged with the second pinion P2. The second sun gear S2 acts as a fourth rotation element N4, the second planet carrier PC2 acts as a fifth rotation element N5, and the second ring gear R2 acts as a sixth rotation element N6.

The third planetary gear set PG3 is a single pinion planetary gear set, and includes a third sun gear S3, a third planet carrier PC3 that supports a third pinion P3 externally engaged with the third sun gear S3, and a third ring gear R3 internally engaged with the third pinion P3. The third sun gear S3 acts as a seventh rotation element N7, the third planet carrier PC3 acts as an eighth rotation element N8, and the third ring gear R3 acts as a ninth rotation element N9.

The fourth planetary gear set PG4 is a single pinion planetary gear set, and includes a fourth sun gear S4, a fourth planet carrier PC4 that supports a fourth pinion P4 externally engaged with the fourth sun gear S4, and a fourth ring gear R4 internally engaged with the fourth pinion P4. The fourth sun gear S4 acts as a tenth rotation element N10, the fourth planet carrier PC4 acts as an eleventh rotation element N11, and the fourth ring gear R4 acts as a twelfth rotation element N12.

In the arrangement of the first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, the second rotation element N2 is directly connected with the ninth rotation element N9 and the tenth rotation element N10, and the fifth rotation element N7 is directly connected with the twelfth rotation element N12, by nine connecting members TM1 to TM9.

The nine connecting members TM1 to TM9 are arranged as follows.

The first connecting member TM1 is connected with the first rotation element N1 (first sun gear S1).

The second connecting member TM2 is connected with the second rotation element N2 (first planet carrier PC1), the ninth rotation element N9 (third ring gear R3), and the tenth rotation element N10 (fourth sun gear S4).

The third connecting member TM3 is connected with the third rotation element N3 (first ring gear R1), and directly connected with the input shaft IS, thereby enabling the third rotation element N3 (first ring gear R1) to continuously act as an input element.

The fourth connecting member TM4 is connected with the fourth rotation element N4 (second sun gear S2), and directly connected with the transmission housing H, thereby enabling the fourth rotation element N4 (second sun gear S2) to continuously act as a fixed element.

The fifth connecting member TM5 is connected with the fifth rotation element N5 (second planet carrier PC2) and the twelfth rotation element N12 (fourth ring gear R4), and directly connected with the output shaft OS, thereby enabling the twelfth rotation element N12 (fourth ring gear R4) to continuously act as an output element.

The sixth connecting member TM6 is connected with the sixth rotation element N6 (second ring gear R2), and selectively connectable with the second connecting member TM2.

The seventh connecting member TM7 is connected with the seventh rotation element N7 (third sun gear S3), selectively connectable with the input shaft IS and the first connecting member TM1, and selectively connectable with the transmission housing H.

The eighth connecting member TM8 is connected with the eighth rotation element N8 (third planet carrier PC3), and selectively connectable with the transmission housing H.

The ninth connecting member TM9 is connected with the eleventh rotation element N11 (fourth planet carrier PC4), and selectively connectable with the input shaft IS.

The connecting members TM1 to TM9 may be selectively interconnected with one another by control elements of four clutches C1, C2, C3, and C4.

The connecting members TM1 to TM9 may be selectively connectable with the transmission housing H, by control elements of two brakes B1 and B2.

The six control elements C1 to C4 and B1 to B2 are arranged as follows.

The first clutch C1 is arranged between the input shaft IS and the seventh connecting member TM7, such that the input shaft IS and the seventh connecting member TM7 may selectively become integral.

The second clutch C2 is arranged between the input shaft IS and the ninth connecting member TM9, such that the input shaft IS and the ninth connecting member TM9 may selectively become integral.

The third clutch C3 is arranged between the second connecting member TM2 and the sixth connecting member TM6, such that the second connecting member TM2 and the sixth connecting member TM6 may selectively become integral.

The fourth clutch C4 is arranged between the first connecting member TM1 and the seventh connecting member TM7, such that the first connecting member TM1 and the seventh connecting member TM7 may selectively become integral.

The first brake B1 is arranged between the seventh connecting member TM7 and the transmission housing H, such that the seventh connecting member TM7 may selectively act as a fixed element.

The second brake B2 is arranged between the eighth connecting member TM8 and the transmission housing H, such that the eighth connecting member TM8 may selectively act as a fixed element.

The control elements of the first, second, third, and fourth clutches C1, C2, C3, and C4 and the first and second brakes B1 and B2 may be realized as multi-plate hydraulic pressure friction devices that are frictionally engaged by hydraulic pressure.

FIG. 2 is an operational chart for respective control elements at respective shift stages in a planetary gear train according to various embodiments of the present invention.

As shown in FIG. 2, a planetary gear train according to various embodiments of the present invention performs shifting by operating three control elements at respective shift stages.

In the first forward speed D1, the third and fourth clutches C3 and C4 and the second brake B2 are operated. As a result, the second connecting member TM2 is interconnected with the sixth connecting member TM6 by the operation of the third clutch C3, and the first connecting member TM1 is interconnected with the seventh connecting member TM7 by the operation of the fourth clutch C4. In this state, torque is input to the third connecting member TM3. In addition, while the fourth connecting member TM4 is acting as a fixed element, the eighth connecting member TM8 simultaneously acts as a fixed element by the operation of the second brake B2, thereby realizing the first forward speed and outputting a shifted torque through the output shaft OS connected with the fifth connecting member TM5.

In the second forward speed D2, the third and fourth clutches C3 and C4 and the first brake B1 are operated. As a result, the second connecting member TM2 is interconnected with the sixth connecting member TM6 by the operation of the third clutch C3, and the first connecting member TM1 is interconnected with the seventh connecting member TM7 by the operation of the fourth clutch C4. In this state, torque is input to the third connecting member TM3. In addition, while the fourth connecting member TM4 is acting as a fixed element, the seventh connecting member TM7 simultaneously acts as a fixed element by the operation of the first brake B1, thereby realizing the second forward speed and outputting a shifted torque through the output shaft OS connected with the fifth connecting member TM5.

In the third forward speed D3, the first, third, and fourth clutches C1, C3, and C4 are operated. As a result, the input shaft IS is interconnected with the seventh connecting member TM7 by the operation of the first clutch C1, the second connecting member TM2 is interconnected with the sixth connecting member TM6 by the operation of the third clutch C3, and the first connecting member TM1 is interconnected with the seventh connecting member TM7 by the operation of the fourth clutch C4. In this state, torque is simultaneously input to the third connecting member TM3 and the seventh connecting member TM7. In addition, the fourth connecting member TM4 acts as a fixed element, thereby realizing the third forward speed and outputting a shifted torque through the output shaft OS connected with the fifth connecting member TM5.

In the fourth forward speed D4, the first, second, and third clutches C1, C2, and C3 are operated. As a result, the input shaft IS is interconnected with the seventh connecting member TM7 by the operation of the first clutch C1, the input shaft IS is interconnected with the ninth connecting member TM9 by the operation of the second clutch C2, and the second connecting member TM2 is interconnected with the sixth connecting member TM6 by the operation of the third clutch C3. In this state, torque is simultaneously input to the third, seventh, and ninth connecting members TM3, TM7, and TM9. In addition, the fourth connecting member TM4 acts as a fixed element, thereby realizing the fourth forward speed and outputting a shifted torque through the output shaft OS connected with the fifth connecting member TM5.

In the fifth forward speed D5, the first, second, and fourth clutches C1, C2, and C4 are operated. As a result, the input shaft IS is interconnected with the seventh connecting member TM7 by the operation of the first clutch C1, the input shaft IS is interconnected with the ninth connecting member TM9 by the operation of the second clutch C2, and the first connecting member TM1 is interconnected with the seventh connecting member TM7 by the operation of the fourth clutch C4. In this state, torque is simultaneously input to the third, seventh, and ninth connecting member TM3, TM7, and TM9. In addition, the fourth connecting member TM4 acts as a fixed element, thereby realizing the fifth forward speed and outputting a shifted torque through the output shaft OS connected with the fifth connecting member TM5.

In the sixth forward speed D6, the second and fourth clutches C2 and C4 and the first brake B1 are operated. As a result, the input shaft IS is interconnected with the ninth connecting member TM9 by the operation of the second clutch C2, and the first connecting member TM1 is interconnected with the seventh connecting member TM7 by the operation of the fourth clutch C4. In this state, torque is simultaneously input to the third connecting member TM3 and the ninth connecting member TM9. In addition, while the fourth connecting member TM4 is acting as a fixed element, the seventh connecting member TM7 simultaneously acts as a fixed element by the operation of the first brake B1, thereby realizing the sixth forward speed and outputting a shifted torque through the output shaft OS connected with the fifth connecting member TM5.

In the seventh forward speed D7, the second and fourth clutches C2 and C4 and the second brake B2 are operated. As a result, the input shaft IS is interconnected with the ninth connecting member TM9 by the operation of the second clutch C2, and the first connecting member TM1 is interconnected with the seventh connecting member TM7 by the operation of the fourth clutch C4. In this state, torque is simultaneously input to the third connecting member TM3 and the ninth connecting member TM9. In addition, while the fourth connecting member TM4 is acting as a fixed element, the eighth connecting member TM8 simultaneously acts as a fixed element by the operation of the second brake B2, thereby realizing the seventh forward speed and outputting a shifted torque through the output shaft OS connected with the fifth connecting member TM5.

In the eighth forward speed D8, the second clutch C2 and the first and second brakes B1 and B2 are operated. As a result, the input shaft IS is interconnected with the ninth connecting member TM9 by the operation of the second clutch C2. In this state, torque is simultaneously input to the third connecting member TM3 and the ninth connecting member TM9. In addition, while the fourth connecting member TM4 is acting as a fixed element, the seventh and eighth connecting members TM7 and TM8 simultaneously operate as fixed elements by the operation of the first and second brakes B1 and B2, thereby realizing the eighth forward speed and outputting a shifted torque through the output shaft OS connected with the fifth connecting member TM5.

In the ninth forward speed D9, the first and second clutches C1 and C2 and the second brake B2 are operated. As a result, the input shaft IS is interconnected with the seventh connecting member TM7 by the operation of the first clutch C1, and the input shaft IS is interconnected with the ninth connecting member TM9 by the operation of the second clutch C2. In this state, torque is simultaneously input to the third, seventh, and ninth connecting members TM3, TM7, and TM9. In addition, while the fourth connecting member TM4 is acting as a fixed element, the eighth connecting member TM8 simultaneously acts as a fixed element by the operation of the second brake B2, thereby realizing the ninth forward speed and outputting a shifted torque through the output shaft OS connected with the fifth connecting member TM5.

In the reverse speed REV, the first and third clutches C1 and C3 and the second brake B2 are operated. As a result, the input shaft IS is interconnected with the seventh connecting member TM7 by the operation of the first clutch C1, and the second connecting member TM2 is interconnected with the sixth connecting member TM6 by the operation of the third clutch C3. In this state, torque is simultaneously input to the third and seventh connecting members TM3 and TM7. In addition, while the fourth connecting member TM4 is acting as a fixed element, the eighth connecting member TM8 simultaneously acts as a fixed element by the operation of the second brake B2, thereby realizing the reverse speed and outputting a shifted torque through the output shaft OS connected with the fifth connecting member TM5.

As described above, a planetary gear train according to various embodiments of the present invention realizes at least nine forward speeds and at least one reverse speed formed by operating the four planetary gear sets PG1, PG2, PG3, and PG4 by controlling the four clutches C1, C2, C3, and C4 and the two brakes B1 and B2.

In addition, a planetary gear train according to various embodiments of the present invention realizes a gear ratio span of more than 8.0, thereby maximizing efficiency of driving an engine.

Furthermore, a planetary gear train according to various embodiments of the present invention achieves step ratios of more than 1.2 for all shifting except for forward 6/7 and 7/8 shifting and realizes linearity of step ratios, thereby improving drivability, e.g., acceleration quality before and after shifting and engine speed rhythm.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. A planetary gear train of an automatic transmission for a vehicle, comprising: an input shaft to receive an engine torque; an output shaft to output a shifted torque; a first planetary gear set including a first rotation element, a second rotation element, and a third rotation element; a second planetary gear set including a fourth rotation element, a fifth rotation element, and a sixth rotation element; a third planetary gear set including a seventh rotation element, an eighth rotation element, and a ninth rotation element; a fourth planetary gear set including a tenth rotation element, an eleventh rotation element, and a twelfth rotation element; and six control elements for selectively interconnecting the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, and twelfth rotation elements and a transmission housing, wherein the input shaft is continuously connected with the third rotation element, the output shaft is continuously connected with the twelfth rotation element, the fourth rotation element is directly connected with the transmission housing, the second rotation element is continuously connected with the ninth rotation element, the second rotation element is continuously connected with the tenth rotation element, the fifth rotation element is continuously connected with the twelfth rotation element, the seventh rotation element is selectively connectable with the transmission housing, and three control elements of the six control elements are operated to achieve at least nine forward speeds and at least one reverse speed.
 2. The planetary gear train of claim 1, wherein the eighth rotation element is selectively connectable with the transmission housing; the input shaft is selectively connectable with the seventh rotation element; the input shaft is selectively connectable with the eleventh rotation element; the second rotation element is selectively connectable with the sixth rotation element; and the first rotation element is selectively connectable with the seventh rotation element.
 3. The planetary gear train of claim 1, wherein the first rotation element, the second rotation element, and the third rotation element comprise a sun gear, a planet carrier, and a ring gear of the first planetary gear set; the fourth rotation element, the fifth rotation element, and the sixth rotation element comprise a sun gear, a planet carrier, and a ring gear of the second planetary gear set; the seventh rotation element, the eighth rotation element, and the ninth rotation element comprise a sun gear, a planet carrier, and a ring gear of the third planetary gear set; and the tenth rotation element, the eleventh rotation element, and the twelfth rotation element comprise a sun gear, a planet carrier, and a ring gear of the fourth planetary gear set.
 4. A planetary gear train of an automatic transmission for a vehicle, comprising: an input shaft receiving an engine torque; an output shaft outputting a shifted torque; a first planetary gear set including a first rotation element, a second rotation element, and a third rotation element; a second planetary gear set including a fourth rotation element, a fifth rotation element, and a sixth rotation element; a third planetary gear set including a seventh rotation element, an eighth rotation element, and a ninth rotation element; a fourth planetary gear set including a tenth rotation element, an eleventh rotation element, and a twelfth rotation element; six control elements for selectively interconnecting the rotation elements and a transmission housing; a first connecting member connected with the first rotation element; a second connecting member connected with the second rotation element, the ninth rotation element, and the tenth rotation element; a third connecting member connected with the third rotation element and directly connected with the input shaft; a fourth connecting member connected with the fourth rotation element and directly connected with the transmission housing; a fifth connecting member connected with the fifth rotation element and the twelfth rotation element and directly connected with the output shaft; a sixth connecting member connected with the sixth rotation element and selectively connectable with the second connecting member; a seventh connecting member connected with the seventh rotation element, selectively connectable with the input shaft and the first connecting member, and selectively connectable with the transmission housing; an eighth connecting member connected with the eighth rotation element and selectively connectable with the transmission housing; and a ninth connecting member connected with the eleventh rotation element and selectively connectable with the input shaft.
 5. The planetary gear train of claim 4, wherein the first planetary gear set comprises a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear, where the first rotation element is the first sun gear, the second rotation element is the first planet carrier, and the third rotation element is the first ring gear; the second planetary gear set comprises a single pinion planetary gear set including a second sun gear, a second planet carrier, and a second ring gear, where the fourth rotation element is the second sun gear, the fifth rotation element is the second planet carrier, and the sixth rotation element is the second ring gear; the third planetary gear set comprises a single pinion planetary gear set including a third sun gear, a third planet carrier, and a third ring gear, where the seventh rotation element is the third sun gear, the eighth rotation element is the third planet carrier, and the ninth rotation element is the third ring gear; and the fourth planetary gear set comprises a single pinion planetary gear set including a fourth sun gear, a fourth planet carrier, and a fourth ring gear, where the tenth rotation element is the fourth sun gear, the eleventh rotation element is the fourth planet carrier, and the twelfth rotation element is the fourth ring gear.
 6. The planetary gear train of claim 4, wherein the six control elements comprise: a first clutch selectively connecting the input shaft and the seventh connecting member; a second clutch selectively connecting the input shaft and the ninth connecting member; a third clutch selectively connecting the second connecting member and the sixth connecting member; a fourth clutch selectively connecting the first connecting member and the seventh connecting member; a first brake selectively connecting the seventh connecting member and the transmission housing; and a second brake selectively connecting the eighth connecting member and the transmission housing.
 7. The planetary gear train of claim 6, wherein shift stages realized by selective operation of the six control elements comprise: a first forward speed realized by operation of the third and fourth clutches and the second brake; a second forward speed realized by operation of the third and fourth clutches and the first brake; a third forward speed realized by operation of the first, third, and fourth clutches; a fourth forward speed realized by operation of the first, second, and third clutches; a fifth forward speed realized by operation of the first, second, and fourth clutches; a sixth forward speed realized by operation of the second and fourth clutches and the first brake; a seventh forward speed realized by operation of the second and fourth clutches and the second brake; an eighth forward speed realized by operation of the second clutch and the first and second brakes; a ninth forward speed realized by operation of the first clutch and the second clutch and the second brake; and a reverse speed realized by operation of the first and third clutches and the second brake.
 8. A planetary gear train of an automatic transmission for a vehicle, comprising: an input shaft for receiving an engine torque; an output shaft for outputting a shifted torque; a first planetary gear set comprising a single pinion planetary gear set including a first rotation element, a second rotation element, and a third rotation element; a second planetary gear set comprising a single pinion planetary gear set including a fourth rotation element, a fifth rotation element, and a sixth rotation element; a third planetary gear set comprising a single pinion planetary gear set including a seventh rotation element, an eighth rotation element, and a ninth rotation element; a fourth planetary gear set comprising a single pinion planetary gear set including a tenth rotation element, an eleventh rotation element, and a twelfth rotation element; a first connecting member connected with the first rotation element; a second connecting member connected with the second rotation element, the ninth rotation element, and the tenth rotation element; a third connecting member connected with the third rotation element and directly connected with the input shaft; a fourth connecting member connected with the fourth rotation element and directly connected with the transmission housing; a fifth connecting member connected with the fifth rotation element and the twelfth rotation element and directly connected with the output shaft; a sixth connecting member connected with the sixth rotation element and selectively connectable with the second connecting member; a seventh connecting member connected with the seventh rotation element, selectively connectable with the input shaft and the first connecting member, and selectively connectable with the transmission housing; an eighth connecting member connected with the eighth rotation element and selectively connectable with the transmission housing; a ninth connecting member connected with the eleventh rotation element and selectively connectable with the input shaft; a first clutch selectively connecting the input shaft and the seventh connecting member; a second clutch selectively connecting the input shaft and the ninth connecting member; a third clutch selectively connecting the second connecting member and the sixth connecting member; a fourth clutch selectively connecting the first connecting member and the seventh connecting member; a first brake selectively connecting the seventh connecting member and the transmission housing; and a second brake selectively connecting the eighth connecting member and the transmission housing.
 9. The planetary gear train of claim 8, wherein the first planetary gear set includes a first sun gear, a first planet carrier, and a first ring gear, where the first rotation element is the first sun gear, the second rotation element is the first planet carrier, and the third rotation element is the first ring gear; the second planetary gear set includes a second sun gear, a second planet carrier, and a second ring gear, where the fourth rotation element is the second sun gear, the fifth rotation element is the second planet carrier, and the sixth rotation element is the second ring gear; the third planetary gear set includes a third sun gear, a third planet carrier, and a third ring gear, where the seventh rotation element is the third sun gear, the eighth rotation element is the third planet carrier, and the ninth rotation element is the third ring gear; and the fourth planetary gear set includes a fourth sun gear, a fourth planet carrier, and a fourth ring gear, where the tenth rotation element is the fourth sun gear, the eleventh rotation element is the fourth planet carrier, and the twelfth rotation element is the fourth ring gear.
 10. The planetary gear train of claim 8, wherein shift stages realized by selective operation of the four clutches and two brakes comprise: a first forward speed realized by operation of the third and fourth clutches and the second brake; a second forward speed realized by operation of the third and fourth clutches and the first brake; a third forward speed realized by operation of the first, third, and fourth clutches; a fourth forward speed realized by operation of the first, second, and third clutches; a fifth forward speed realized by operation of the first, second, and fourth clutches; a sixth forward speed realized by operation of the second and fourth clutches and the first brake; a seventh forward speed realized by operation of the second and fourth clutches and the second brake; an eighth forward speed realized by operation of the second clutch and the first and second brakes; a ninth forward speed realized by operation of the first clutch and the second clutch and the second brake; and a reverse speed realized by operation of the first and third clutches and the second brake.
 11. A planetary gear train of an automatic transmission for a vehicle, comprising: an input shaft for receiving an engine torque; an output shaft for outputting a shifted torque; a first planetary gear set comprising a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear; a second planetary gear set comprising a single pinion planetary gear set including a second sun gear, a second planet carrier, and a second ring gear; a third planetary gear set comprising a single pinion planetary gear set including a third sun gear, a third planet carrier, and a third ring gear; a fourth planetary gear set comprising a single pinion planetary gear set including a fourth sun gear, a fourth planet carrier, and a fourth ring gear; a first connecting member connected with the first sun gear; a second connecting member connected with the first planet carrier, the third ring gear, and the fourth sun gear; a third connecting member connected with the first ring gear and directly connected with the input shaft; a fourth connecting member connected with the second sun gear and directly connected with a transmission housing; a fifth connecting member connected with the second planet carrier and the fourth ring gear and directly connected with the output shaft; a sixth connecting member connected with the second ring gear and selectively connectable with the second connecting member; a seventh connecting member connected with the third sun gear, selectively connectable with the input shaft and the first connecting member, and selectively connectable with the transmission housing; an eighth connecting member connected with the third planet carrier and selectively connectable with the transmission housing; a ninth connecting member connected with the fourth planet carrier and selectively connectable with the input shaft; and six control elements for selectively interconnecting the first, second, third, fourth, fifth, sixth, seventh, eighth, and ninth connecting members and the transmission housing.
 12. The planetary gear train of claim 11, wherein the six control elements comprise: a first clutch selectively connecting the input shaft and the seventh connecting member; a second clutch selectively connecting the input shaft and the ninth connecting member; a third clutch selectively connecting the second connecting member and the sixth connecting member; a fourth clutch selectively connecting the first connecting member and the seventh connecting member; a first brake selectively connecting the seventh connecting member and the transmission housing; and a second brake selectively connecting the eighth connecting member and the transmission housing.
 13. The planetary gear train of claim 12, wherein shift stages realized by selective operation of the six control elements comprise: a first forward speed realized by operation of the third and fourth clutches and the second brake; a second forward speed realized by operation of the third and fourth clutches and the first brake; a third forward speed realized by operation of the first, third, and fourth clutches; a fourth forward speed realized by operation of the first, second, and third clutches; a fifth forward speed realized by operation of the first, second, and fourth clutches; a sixth forward speed realized by operation of the second and fourth clutches and the first brake; a seventh forward speed realized by operation of the second and fourth clutches and the second brake; an eighth forward speed realized by operation of the second clutch and the first and second brakes; a ninth forward speed realized by operation of the first clutch and the second clutch and the second brake; and a reverse speed realized by operation of the first and third clutches and the second brake. 